Wireless energy transfer is useful in cases where the interconnection of wires may be inconvenient, hazardous or impossible. In recent years, applications employing near-field wireless power and/or data transmission have gained prominence in areas such as consumer electronics, medical systems, military systems and industrial applications. Near-field communication enables the transfer of electrical energy and/or data wirelessly through magnetic field induction between a transmitting antenna and a corresponding receiving antenna. Near-field communication interface and protocol modes are defined by ISO/IEC standard 18092.
However, near-field communication is often not optimal because prior art antennas that facilitate the wireless transfer of electrical power and/or data operate inefficiently. In such cases, the amount of electrical energy received by the corresponding antenna is generally significantly less than the amount of electrical energy initially transmitted. In addition, data that is received may be incomplete or may become corrupted. In addition, near-field communication generally suffers from reduced wireless transfer distances, i.e., the transmission range, and physical antenna orientation issues. These inefficiencies of near field communication are largely due to the low quality factor of the prior art antennas in addition to the inefficient large size of prior art antennas. In general, prior art near field communication antennas have a relatively large size that hinders efficient operation and wireless transmission. Size and efficiency are often a tradeoff, a problem which becomes more acute when multiple wireless operations are desired, i.e., multiple modes of operation. A solution to inefficient near-field communication is antenna integration.
Inductive solutions transfer power and/or data between two inductor coils that are placed in close proximity to each other. This technology, for example, facilitates the deployment of inductive charging “hot spots” that enables wireless electrical charging of electronic devices by simply placing them near a charging “hot spot”, such as on a surface of a table. However, for these systems to operate efficaciously, the respective transmitter and receiver antennas are required to not only be located in close proximity to each other but, in addition, must also be physically positioned in a specific orientation with respect to one another. Typically, these prior art antennas require that they are physically positioned in near perfect alignment such that the centers of the respective transmitting and receiving antennas are oriented in perfect opposition to each other in order to operate efficaciously. This general requirement for near perfect physical alignment of the transmitting and receiving antennas typically leads to poor near field communication performance as it is challenging to achieve perfect alignment of the opposing transmitting and receiving antennas to ensure proper wireless power and/or data transfer.
As a result, use of these prior art antennas leads to near field communication that is generally not reliable and significantly reduced operating efficiency. As defined herein “inductive charging” is a wireless charging technique that utilizes an alternating electromagnetic field to transfer electrical power between two antennas. “Resonant inductive coupling” is defined herein as the near field wireless transmission of electrical energy between two magnetically coupled coils that are part of two spaced apart resonant circuits that are tuned to resonate at the same frequency. “Magnetic resonance” is defined herein as the excitation of particles (as atomic nuclei or electrons) in a magnetic field by exposure to electromagnetic radiation of a specific frequency.
Various multimode wireless power solutions have been developed to address these antenna positioning and proximity limitations and concomitant of reliability & efficiency issues. In some cases, operating frequency bands have been reduced, for example, a frequency band that ranges from about 150 kHz to about 250 kHz to increase range from about 15 mm to about 20 mm has been achieved by resonating the receiving antenna at a frequency that is about the same as the frequency of the transmitting antenna, both of which are similar to the frequency at which power transfer is taking place. However, such solutions have not sufficiently addressed the need to provide increased efficient wireless transfer with multiple mode operation capability through modification of the antenna structure.
Inductive and resonance interface standards have been developed to create global standards for wireless charging technologies. “Qi” is a wireless inductive power transfer standard/specification. Specifically, the Qi wireless inductive power transfer standard is an interface standard that was developed by the Wireless Power Consortium. The Qi interface standard is a protocol generally intended to facilitate transfer of low electrical power up to about 15 W at frequencies ranging from 100 kHz to about 200 kHz over distances ranging from about 2 mm to about 5 mm.
“Rezence” is a competing interface standard developed by the Alliance for Wireless Power (A4WP) for wireless electrical power transfer based on the principles of magnetic resonance. Specifically, the Rezence interface standard currently supports electrical power transfer up to about 50 W, at distances up to about 5 cm. Unlike the Qi interface standard, the Rezence interface standard utilizes an increased frequency of about 6.78 MHz+/−15 kHz.
In addition, there exists a third standard developed by the Power Matters Alliance (PMA) that operates in the frequency range of about 100 kHz to about 350 kHz. Unlike prior art multi-band antennas, the multi-band single structure antenna of the present disclosure is capable of receiving and/or transmitting signals and/or electrical energy across all of these standards with one antenna.
Currently these standards are the preeminent standards for wireless power technology in consumer electronics. Although these standards are relatively new to the market, the surge in development of small portable wireless devices and the proliferation of wireless transmission solutions into other wireless applications increases the need for, and adoption of, these standards. The Qi interface standard, released in 2010, has already been widely adopted. The Qi interface standard is currently incorporated into more than 20 million products world-wide.
Antennas are a key building block in the construction of wireless power and/or data transmission systems. As wireless technologies have developed, antennas have advanced from a simple wire dipole to more complex structures. Mutli-mode antennas have been designed to take advantage of different wireless interface standards. For example, Qi inductive wireless charging was first demonstrated in an Android smartphone more than four years ago. In 2015, the Samsung® Galaxy S6® supports two wireless charging standards, namely PMA and WPC's Qi. This solution, however, addresses inductive interface standards only. Given the differences in, for example, performance efficiencies, size, transfer range, and positioning freedom between inductive transmission versus resonance-based transmission, what is needed is a single antenna board that works with all types of wireless charging standards, for example, the PMA standard, WPC's Qi standard and A4WP's Rezence standard.
Furthermore, some wireless transmission applications will utilize a combination of standards-based and/or non-standards-based transfer protocols. The multi-band single structure antenna of the present disclosure is capable of receiving and/or transmitting signals and/or electrical energy across any combination of standards-based and/or non-standards-based transfer protocols with one antenna.
Prior art “multi mode” antennas, referred to as “Two-Structure Dual Mode” (TSDM) antennas, are typically constructed having two discrete antenna structures that are positioned on a substrate. The two discrete antenna structures that comprise a TSDM antenna operate independent of each other and require separate terminal connections to each of the respective independent antenna. FIG. 1 illustrates an example of such a prior art two-structure dual mode antenna 10 which comprises a first exterior inductor 12 and a second, separate interior inductor 14, each antenna having a positive and negative terminal connection respectively that are not electrically connected. However, such TSDM antennas have a relatively large footprint which comprises a significant amount of space and surface area. Such TSDM antennas are therefore, not ideally suited for incorporation with small electronic devices or positioned within small confined spaces.
Two-structure multi-mode (TSMM) antennas 10 are generally constructed such that both the separate exterior and interior inductors 12, 14 each have a specific inductance. Thus, the exterior inductor 12 is constructed having a specific number of exterior inductor turns and the interior inductor 14 is constructed having a specific number of interior inductor turns. In this structure, the two respective coils operate as independent antennas. Coil-based TSMM antennas fundamentally require a large amount of area to enable better performance. Specifically, antenna coupling between the exterior and interior antennas require that they be positioned a distance away from each other such that energy generated from one antenna is not absorbed by the other. Furthermore, in a traditional TSMM configuration, when the “interior” antenna is operating, the area extending from the outermost trace of the internal antenna to the outermost trace of the exterior antenna is not being utilized and, thus, is “wasted” space.